Rate of Growth in Gobius minutua. 231 



Scales. 



The scales of the species of gobies examined are invariably 

 ctenoid ; but as those of the various species differ in many- 

 respects from one another, they will be dealt with in turn 

 later. The scales are always closely applied to the skin : they 

 are slightly corrugated, but their margins are generally entire. 

 Unfortunately the majority of the gobies in the collection were 

 destitute of scales. Whether this was due to rough treatment 

 in the trawl or to the action of the preservative in which the 

 fish had been kept there is some doubt ; but as there were 

 usually a considerable number of loose scales in the bottles, 

 the latter is the more probable cause. The fishes preserved 

 in spirit retain their scales in a more satisfactory manner than 

 those preserved in formaline. 



The most striking feature about the scales of gobies is the 

 uniform character of the concentric rings. These are very 

 clearly marked from the youngest stages, and although many 

 of the rings may be discontinuous or even intersecting in 

 pairs, there is a mathematical precision about their arrange- 

 ment which defies attempts to define the limit between summer 

 and winter growths. Hoff bauer found that in the case of the 

 carp the number of concentric rings representing a given 

 period of growth did not vary much in scales taken from 

 corresponding parts of the same fish. This is not so in the 

 case of G. minutus, for on four adjacent scales of a 75 mm. 

 specimen 32, 26, 18, 16 concentric rings were counted. 

 Adjacent scales taken from examples of other species of 

 Gobius, however, show but very slight variation in the 

 number of concentric rings, especially in the younger stages. 

 From the data given under the heading of the various species, 

 it seems probable that there is absolutely no relation between 

 the number of concentric rings on the scale of a goby and the 

 length of the fish from which the scale was taken. In other 

 words the number of rings on the scale is no criterion for 

 estimating the age of a goby. Few, if any, writers on the 

 subject ever put confidence in the number of rings on the 

 scale as an aid to age identification in the larger fishes, but it 

 seemed possible that in these short-lived forms an approxi- 

 mate relationship might be found. Hoffbauer cites the case 

 of a carp, living under unfavourable conditions, whose scales 

 showed a very even distribution of the concentric rings. That 

 is to say, a fish which usually shows most clearly on its scales 

 the varying width between the rings due to the varying con- 

 ditions of environment, when transferred to uniform conditions 

 of environment showed uniform width between the concentric 



